Files don't copy correctly from one computer to another

Actually, all files. Pictures, data files of all types, .pdf files, all of them.

I just set up a new I Mac, migrated all my files, apps and data to it from my MacBook Pro Retina, and use both computers for accounting work, so I need to copy files back and forth. I have a folder on both called Files and I keep all my data files in that folder and copy it back and forth. I can copy from the IMac to the MacBook Pro, no request for a password, etc, but when I try to copy anything from the MacBook Pro to the I Mac, it requests a password and it only copies a shell of a file with -0- bytes of content, in other words, name only. Sure would appreciate any suggestions or help.

Thanks

WiFi, on the same network. I also have them connected with a Thunderbolt cable, as I use screen sharing, but it is off at the time of copying the files.